D010 refinement_violated

A runtime defect: the running program stops with it; no compile phase reports it, and try cannot catch it. sakura explain D010 prints this explanation offline.

A checked introduction such as Email.from(s) received a value that fails the refinement. Use validate (which returns a typed error) at untrusted boundaries.

Runtime defects come from running programs, so compiler/tests/ui has no fixture for them; the explanation above names the repair.